1. Field of the Invention
This invention relates to an improvement of a spark plug for an internal combustion engine.
2. Prior Art
Spark plugs have long been used in an internal combustion engine to ignite combustible gas within the cylinder. These spark plugs typically include a ground electrode having a flange which is supported in a spaced relationship by a rectangular support from a center electrode. During ignition electrons move between the electrodes to ignite the combustible gasses in the cylinder. A flame front is formed around the spark and moves outwardly from the spark towards the walls of the cylinder. In order to maximize the efficiency of the combustion to maximize the power from the ignition and to minimize emissions, it is desirable to provide the fastest possible speed in the movement of the flame front. It has also been found that efficiency of the burn can be reduced by a shadow in the flame front formed by the rectangular support of the ground electrode. The electrode blocks the flame front as it expands outwardly from the spark and causes a xe2x80x9cshadow areaxe2x80x9d behind the support where the combustible gas is not efficiently or quickly burned. This slows the burning and resulting in a diminution of the power available from the combustion of the fuel. A high efficiency plug, known as the Splitfire plug, which is disclosed in U.S. Pat. No. 5,280,214, has a ground electrode with a xe2x80x9cYxe2x80x9d shaped electrode. It has been found that carbon collects in the crotch thereby reducing the efficiency of the plug.
Because of the increased cost of fuel and necessity of minimizing the emissions from internal combustion engines, it is desirable to provide a spark plug which maximizes the efficiency of the burn of the combustible gases.
Accordingly, it is an object of the present invention to provide a spark plug which produces a maximum flame front speed and expansion time.
It is a further object of the present invention to provide a spark plug which reduces or eliminates electrode shadow.
It is still another object of the present invention to provide a spark plug which produces an increase in engine power, fuel efficiency, and minimizes the emissions.
A further object of the invention is to provide a spark plug which is simple in structure and inexpensive to manufacture.
Accordingly it has been found that flame propagation can be maximized by providing a spark plug which produces a spherical flame kernel which is unimpeded by electrode shadow or carbon collection. The spark plug includes a ground electrode which includes a loop supported by a pair of stanchions. The ground electrode has a circular cross section of minimum mass and is contoured to avoid any sharp points. The loop is spaced apart from a center electrode and has a center circular portion extending through an arc of approximately 270xc2x0. The loop is connected to the stanchions by support portions which curve together to a position radially outward with respect to the circular portion to define a narrow gap. The gap prevents formation of a carbon collection area. An arch portion curves outwardly and downwardly through an arc approximately 90xc2x0 to extend between the support portions and the stanchions. The stanchions extend in a direction coaxial with the axis of the spark plug to a metal end of the plug. The stanchions are separated through an arc of approximately 90xc2x0. In the preferred embodiment the electrode is formed of a single wire having a minimum diameter as small as possible to maintain the shape. For most suitable metals such as alloys of nickel and cobalt the diameter of the wire is in the range of 0.030 inches plus or minus 0.015 inches.
The ground electrode promotes rapid propagation of the spark kernel and enhanced plasma expansion while presenting a minimum obstruction from the mass of the ground electrode. The circular cross section and contoured shape presents no sharp points and provides for fast heat sink properties. The thin wire stanchions minimize shadow to produce combustion of higher efficiency than other known spark plugs. The spark plug produces substantially increased torque, horse power and fuel economy while reducing carbon dioxide, carbon monoxide, oxides of nitrogen and hydrocarbon emissions.